Do vaccines trigger diseases they should prevent?

A writer called “A Midwestern Doctor,” who has connections to Mercola, claims in a Substack article that vaccines can cause the same diseases they are supposed to prevent.

Vaccines do not cause the diseases they are made to prevent. There are different kinds of vaccines, and they work in different ways. None of them causes the diseases they are supposed to prevent.

Some vaccines use a live but weakened germ. “Weakened” means the germ has been changed so it cannot cause the disease in people with healthy immune systems. These are called live attenuated vaccines.

Other vaccines use killed germs or only small pieces of a germ. Most flu shots use inactivated flu viruses. “Inactivated” means the virus has been killed. It cannot grow, spread, or cause the flu.

Vaccines like these cannot grow or spread inside the body. You need a whole germ to grow and spread in order to get sick. A killed germ or a small piece of a germ cannot cause infection because it is not the whole germ. It is only enough to help the immune system learn what the outside part of the real germ looks like. In the future, if the immune system sees these outside parts on the whole germ, it knows what to do next.

The COVID mRNA vaccine is another kind of vaccine. The COVID vaccine does not contain the whole coronavirus. It teaches the body to recognize one piece of the virus, called the spike protein. It does not contain the whole virus, so it cannot give someone COVID.

Some people think one vaccine might cause a different disease. The article talks about cases of polio that happened after people got DTaP vaccines. But those vaccines do not contain poliovirus. A vaccine that does not contain poliovirus cannot cause polio. A person can only get polio if they are exposed to poliovirus.

The author may be mixing up a few different ideas.

One is a breakthrough infection. This is when someone gets sick even though they were vaccinated. That can happen if the vaccine did not fully protect them, or if they were exposed to the germ before their body had enough time to build protection.

Another possibility is coincidence. Sometimes a person is exposed to a disease around the same time they get a vaccine. That does not mean the vaccine caused the illness.

A person can also get sick from a totally different germ around the same time they were vaccinated. For example, if someone gets a pertussis vaccine and later gets polio, the pertussis vaccine did not cause polio. They would have had to be exposed to poliovirus separately.

Vaccines help the immune system learn how to fight certain germs. They do not create diseases out of nowhere, and they cannot cause diseases that are not even in the vaccine.